Basically there are two menu styles Mega Drop Down and Accordion. The menu will choose its style automatically depending on what position it is published on. The themes menu position will give you the horizontal Mega Drop Down style, while the sidebar positions will render the menu using the Accordion style.
In your WordPress administration click on Appearance » Menus and click on the tab of the main menu.
Choose the menu item with the drop down menu you want to customize and click on the small arrow on the right to expand the settings.
There you can set the total of columns you want to have in this menu item’s drop down and the width of each column in pixels.
Using icons in menu items
If you’d like to display icons for drop down menu items, just navigate to the desired level 2 menu item of your Main Menu Appearance » Menus » Your Menu.
Click on the little arrow to expand the menu item settings and type in the path to the icon file in the field Image. Using the relative path to the directory /wp-content/uploads.
Add subtitles to menu items
A subtitle can be added to a menu item by simply placing your subtitle text behind two “|” (pipe) characters. Navigate to Appearance » Menus and select your menu in the tabs on the top. Then, create a new menu item or edit an old one. Place two “|” (pipe) characters behind the title’s caption and enter a text for the subtitle.